vDPA: allow userspace to query features of a vDPA device

This commit adds a new vDPA netlink attribution
VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES. Userspace can query
features of vDPA devices through this new attr.

This commit invokes vdpa_config_ops.get_config()
rather than vdpa_get_config_unlocked() to read
the device config spcae, so no races in
vdpa_set_features_unlocked()

Userspace tool iproute2 example:
$ vdpa dev config show vdpa0
vdpa0: mac 00:e8:ca:11:be:05 link up link_announce false max_vq_pairs 4 mtu 1500
  negotiated_features MRG_RXBUF CTRL_VQ MQ VERSION_1 ACCESS_PLATFORM
  dev_features MTU MAC MRG_RXBUF CTRL_VQ MQ ANY_LAYOUT VERSION_1 ACCESS_PLATFORM
Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Message-Id: <20220929014555.112323-2-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa.c

@@ -820,10 +820,10 @@ static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
 static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
 {
 	struct virtio_net_config config = {};
-	u64 features;
+	u64 features_device, features_driver;
 	u16 val_u16;
 
-	vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config));
+	vdev->config->get_config(vdev, 0, &config, sizeof(config));
 
 	if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac),
 		    config.mac))
@@ -837,12 +837,18 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
 	if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
 		return -EMSGSIZE;
 
-	features = vdev->config->get_driver_features(vdev);
-	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features,
+	features_driver = vdev->config->get_driver_features(vdev);
+	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
+			      VDPA_ATTR_PAD))
+		return -EMSGSIZE;
+
+	features_device = vdev->config->get_device_features(vdev);
+
+	if (nla_put_u64_64bit(msg, VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES, features_device,
 			      VDPA_ATTR_PAD))
 		return -EMSGSIZE;
 
-	return vdpa_dev_net_mq_config_fill(vdev, msg, features, &config);
+	return vdpa_dev_net_mq_config_fill(vdev, msg, features_driver, &config);
 }
 
 static int

include/uapi/linux/vdpa.h

@@ -46,6 +46,7 @@ enum vdpa_attr {
 
 	VDPA_ATTR_DEV_NEGOTIATED_FEATURES,	/* u64 */
 	VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,		/* u32 */
+	/* virtio features that are supported by the vDPA management device */
 	VDPA_ATTR_DEV_SUPPORTED_FEATURES,	/* u64 */
 
 	VDPA_ATTR_DEV_QUEUE_INDEX,              /* u32 */
@@ -54,6 +55,9 @@ enum vdpa_attr {
 
 	VDPA_ATTR_DEV_FEATURES,                 /* u64 */
 
+	/* virtio features that are supported by the vDPA device */
+	VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES,	/* u64 */
+
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,
 };